For many electronic systems, reducing power consumption, all else being equal, is desirable. For example, some electronic systems are battery-powered and power consumption reduction will permit the battery to last longer. Maintaining satisfactory performance levels, however, is also desirable. At times, the desire for reducing power consumption and the desire for higher performance levels are at odds with each other, and tradeoffs are made. That is, a system may sacrifice performance for battery charge longevity, and at other times may sacrifice battery power for performance.
One of the settings in an electronic system that often can be adjusted to vary performance and power consumption is the clock frequency of the processor. A slower clock frequency causes the processor to run slower and thus at a lower performance level but also results in lower power consumption per unit of time. A higher clock frequency results in a higher performance level but also at a higher power consumption level per unit of time. Often, the supply voltage is also scaled for different clock frequencies thereby permitting control over energy or average power consumption.
Some electronic systems may be implemented so as to meet worst-case workload requirements. While the workload need may be relatively low at any point in time (e.g., at night), the possibility exists that the workload need may suddenly spike and thus the system is configured to operate assuming that the worst-case workload need may actually occur. Power is wasted when the system is configured for a higher performance level that is not necessitated by present workload demands.